Granular silicate compositions



Patentecl'oct. 3,1194 4 GRANULAR SILICATE COMPOSITIONS Charles C.Winding, Ithaca, N. Y., assignor to Tide Water Associated Oil Company,Bayonne, N. J., a corporation of Delaware No Drawing. Application June4, 1943,

Serial No. 489,697

8 Claims.

with an aqueous solution containing ions of a suitable metalto replacethe metal of the silicate with the metal of the solutionin a. baseexchange reaction. Obtainment of proper adsorbent structure and otherdesirable physical properties such as hardness of granules in theexchange silicate resulting from the base exchange reaction dependsupon, and is determined by, use in the exchange reaction of a metalsilicate having certain desired properties and structure. Precipitatedsilicate materials prepared by certain controlled operations aresuitable for use in the exchange reaction to obtain exchange silicate adsorbent compositions having the stated desired properties. In oneembodiment, disclosed in my said copending application, a precipitatecontaining calcium silicate is prepared by reacting in hot solution asuitable'sodium silicate with a calcium salt such as calcium chloridewhich may be associated with other substances such as magnesium chloridein the form of certain natural or artificial brines. The calciumsilicate-containing precipitate is washed and then dried sufficientlythat it may be ground to desired particle size. The dried materialisthen preferably ground at this stage to granular particles and screenedto-a size depending upon the use to which the final exchange product isto be put, and the. resulting. screened particles are then treated witha hot solution of a magnesium salt which may consist of theaforementioned brines, to convert, by base exchange reaction, the cal-.cium silicate to magnesium silicate. The 're- 'sulting exchange"magnesium silicate is in granular form, and when properly driedpossesses high adsorbent activity.

One important control factor is the concentrations of the precipitantsused in the preparation of the calcium silicate-containing precipitate.--If concentrations within certain critical limits are used theprecipitate when dried is characterized by a sufliciently hard structurethat it may be ground to granular particles or desired size asaforesaid, and when subjected to the exchange reaction is converted toan highly active granular exchange silicate adsorbent. On the otherhand, precipitates prepared from preclpitants of concentrations outsidethe critical limits result in precipitates which when dried either aretoo soft to be ground to granular size and disintegrate to a powderunsuitable for subsequent conversion to hard granular exchange silicatesby means of the exchange reaction, or they do not possess the properphysical structure for base exchange conversion to highly activegranular adsorbents.

These critical concentration limits vary somewhat depending upon theparticular materials used as precipitants. Concentration limits suitablefor various precipitants are set forth in detail in my copendingapplication, Serial No. 419,109 mentioned hereinabove, as well as mycopending applications Serial No. 389,170, filed April 18, 1941; SerialNo. 419,089, filed November 14, 1941; and Serial No. 426,287, filedJanuary 10, 1942. In general it may be stated that by way of suitableoverall concentrations where precipitated calcium silicate-containingmate- 7 rials are employed in the base exchange reaction theconcentration of the sodium silicate precipitant should be between about0.08 molar and about 0.4 molar (as to. NazO content) and theconcentration of the calcium chloride containing precipitant should bebetween about 0.08 molar and about 0.4 molar (on basis of CaClz plusMgCle present).

The adsorbent compositions described in my said copending applicationsas well as those constituting the subject of the present invention areparticularly adapted for use in percolation decolorizing methods,especially in the percolation decolorization of oils. One importantproperty desired in adsorbents employed in such percolation methods isthat of high resistance to attrition or breakdown of the granularparticles, as will be further explained below,-and the present inventionhas as its principal object the provision of silicate adsorbents havingthis property. In decolorizing oils by percolation treatment a deepstatic bed of adsorbent material is provided through which the oilfilters or percolates. When, by reasonof adsorbing coloring matter fromthe oil, the adsorbent material shows diminished activity, oil flow iscut off. A:fter draining and steaming in situ the adsorbent may beremoved by a suitable conveyor system to a furnace, such as the familiarmultiple hearth, rabble arm type, and revivified by burning. Theadsorbent is then conveyed back to the filtration tanks for re-use.

resistance to attrition will be rduced to an objectionable degree fromits desired particle size to finesf or dust-like material of no value inthe stated use.

The present invention is concerned withiimprovements in the preparationof active granular silicate adsorbent compositions effective to im- Inthe course of these handling operations an adsorbent having low part tothe same special or desired properties and has particular reference tocontrol of the'breakdown characteristics of the product. In generalembodiment, the underlying concept of the in vention is directed tooperating procedure in the production of active base exchange silicatesof the type described in my said copending applications which enablesthe obtainment of optimum or desired degree of resistance to breakdown.This concept, and its useful application to the production of activeexchange silicates, arises from the discovery that resistance tobreakdown or attrition loss of the exchange silicates is related to thewater content of such product and, furthermore, that the particularproportional water content should be relatively low for improvedresistance to breakdown.

The present invention may be adapted to the production of exchangesilicates by the procedure described in my said copending applicationsand outlined hereinabove by controlling the drying conditions employedin drying the silicate product resulting from the exchange reaction. Ihave found that the lower the water content of these exchange silicateproducts the higher the resistance thereof to breakdown, and that bydrying the exchange silicates to relatively low water content certainother desired properties can be obtained in addition to improvedbreakdown resistance. Thus it is possible, by proper drying, to produceadsorbents having desirable combinations of properties.

In general, the stated exchange silicate adsorbents should be dried to awater content of below about 13 per cent. Increase in water contentabove this figureis accompanied by decreases both in adsorbent activityand breakdown resistance. On the other hand, decrease in water contentto below about 13 per cent results in improvement as respects both ofthese factors. The adsorbent activity of the product passes through. apeak or optimum value while the resistance to breakdown continues toimprove, as the water content is decreased. .For example, granularexchange magnesium silicate adsorbents exhibit peak or optimum oildecolorizing power in the percolant method of decolorizing lubricatingoils when they contain from about 8 to about 12 per cent water.

An important feature of the present invention resides in the provisionof exchange silicate adsorbents having in addition to high adsorbentactivity, also superior breakdown resistance. This desirable combinationof properties is obtained by drying the exchange silicates to watercontents which may be even lower than that required for optimumadsorbent activity. Thus in the case ofthe stated granular exchangemagnesium silicate adsorbents it has been found that reduction of watercontent to below 6 per cent results in material improvement in breakdownresistance properties and results in products of entails decreased"throw-away" or discard of fines produced in mechanical handling of theadsorbent. lihus, in the percolant method of decolorizing lubricatingoils referred to hereinabove less quantities of new adsorbent are neededfor replacement purposes during successive periods of use andregeneration.

Illustrating the invention as applied to the stated exchange silicates amagnesium silicatecontaim'ng product was produced according to theprocedure described in my copending applications by reacting in hotaqueous solution a sodium silicate in 0.2 molar concentration (as toNazO content) and a natural brine containing calcium chloride andmagnesium chloride in 0.2 molar concentration (as to calcium chlorideplus magnesium chloride), filtering and washing the resultingprecipitate of calcium silicate material, drying the washed material toa grindable condition, grinding and screening to 30-60 mesh granularparticles and treating said particles with a hot brine containingmagnesium chloride to eiiect replacement of the calcium of saidcaldecolorizing adsorbent with which I am aware and constitute admirablyeffective and satisfactory materials for this purpose. 4

The present invention provides for increased economy in methodsemploying granular adsorbents in that use of the adsorbents hereindisclosed because of their resistance to attrition loss cium silicatewith magnesium. The resulting exchange magnesium silicate granularparticles were then washed and samples thereof were individually driedto various water contents. Each sample was then separately tested todetermine its breakdown resistance.

In the test procedure c. c. of the dried material after being thoroughlyscreened to 3060 mesh range of particle size is placed in the eight inchpan of a standard sieve set together with ten inch steel balls. A coveris placed on the pan and the covered pan is placed in a Ro- Tap sieveshaker. The machine is operated for eight minutes with the tap hammerdisconnected. The material is then removed and screened to obtain theweight per cent passing through a GO-mesh sieve. This percentage istaken as the breakdown under the test conditions described.

The relation between breakdown resistance and water content of theparticular material prepared as above described is shown in the tablehereinbelow, in which the enumerated samples designate the saidmaterial. In the table Breakdown denotes the percentage of materialpassing through a 60-mesh screen after the described test. Thus thelower the "Breakdown"-designated in the table the higher the resistanceof the particu- Sample No. 2332a Breakdown Per cent been found to resultin products of somewhat higher breakdown resistance than those of. the

same water content produced by single-stage dry- Generally anytemperature may be employed in these drying operations which iseffective to remove the desired amount of water without destroying thephysical structure of the product responsible for its adsorbentactivity. Ordinarily temperatures of the drying atmosphere ranging fromabout 250 F. to about 1100 F are satisfactory. Care should be taken,particularly at the higher of these temperatures, to prevent localizedoverheating. This may be accomplished by use of a rotary kiln dryer orother means forsupplying agitation and uniform heating of the product.

I claim:

1. Method for producing-a magnesium silicate composition efieptive as anadsorbent in percolation filtration of lubricating oils which comprisesprecipitating a calcium silicate material from aqueous solution, dryingthe precipitate, treating the dried material with an aqueous solutioncontaining magnesium ions to exchange calcium ions of the calciumsilicate with magnesium ions and drying the resulting magnesium silicateprodnot to a water content of at least about 2 per cent but below about13 per cent.

2. Method defined in claim 1 in which the magnesium silicate product isdried to a water content between about 8 per cent and about 12 per cent.

3. Method defined in claim 1 in which the magcontrolled conditions acalcium silicate material,

nesium silicate product is dried in successive stages.

4. Method defined in claim 1 in which the magnesium silicate product isdried to a water content between about 2 per cent and about 6 per cent.

5. Method defined in claim 1 in which the magnesium silicate productisdried in successi've stages to a water content of between about 8 percent and about 12 per cent.

6. A magnesium silicate composition having oil decolorizing activity andspecially characterized by physical properties including a hardstructure relatively resistanct to attrition, making it suitabl forpercolation oil filtration, said composition having been prepared byprecipitating underdrying said material, treating the dried materialwith an aqueous solution containing magnesium ions to exchange calciumions of the calcium silicate with magnesium ions, and drying theresultmg magnesium silicate product, said magnesium silicate compositionhaving a water content of at least 2 per cent but below about 13 percent.

7. A magnesium silicate composition as described in claim 6 having awater content between about 8 per cent and about 12 per cent.

8. A magnesium silicate composition as described in claim 6 having awater content of at

